The specific aims of the research proposal are directed toward the elucidation of the following major areas of interest: (1) The bacteriophage T3-induced RNA polymerase is being characterized with particular regard to the control mechanisms operating at the level of initiation and termination of RNA synthesis from a T3 DNA template. The following studies are being carried out. a) Determination of the 5'-and the 3' -terminal oligonucleotide sequences of RNA transcripts formed in vitro by T3 RNA polymerase from a T3 DNA template to ascertain the nature of the initiation and termination sequences used by the phage polymerase to initiate and terminate RNA synthesis; b) Studies on the post-transcriptional cleavage by RNase III of high molecular weight in vitro transcripts synthesized by T3 RNA polymerase to small molecular weight transcripts that are identical in size and in 5'- and 3'-oligonucleotide sequences to late mRNAs isolated from T3-infected cells; c) Determination of the map of the major transcription units read by T3 RNA polymerase on T3 genome. (2) Further studies on the molecular mechanisms of initiation of protein synthesis will be carried out along the following directions: a) Identification of active site(s) of initiation factor 2 (IF-2) protein that catalyzes the various discrete steps involved in the polypeptide chain initiation reaction leading to active 70S initiation complex formation: b) Using early and late T3 mRNAs as messenger, we will determine whether there is alteration of host initiation fact 3 in T3 infected cells that leads to preferential translation of late T3 mRNA compared to early T3 mRNA in phage T3-infected cells.